Methane is a common gas that makes up a large proportion of natural gas, which is used for heating, cooking, and other applications. In its naturally occurring state, methane is odorless, tasteless, colorless, and non-toxic. In an enclosed space, however, methane may cause suffocation, if it displaces oxygen. Methane is also flammable and presents a risk of explosion if the gas is not detected and/or controlled.
One type of methane detector includes a thermal conductivity sensor that detects methane by measuring the thermal conductivity of a gaseous mixture. It is a universal practice to calibrate this sensor with pure methane. Calibration with pure methane requires an available methane supply and equipment for storing and delivering it. Also, suitable precautions (e.g. a laboratory exhaust hood, odorization, etc.) must be taken since pure methane raises potential safety concerns.
There is therefore a need for improved methods of calibrating thermal conductivity sensors for a target species (e.g., methane or propane) in a gaseous medium (e.g., air). In particular, there is a need for a method of calibrating such sensors without using the pure target species as a calibration gas.